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sprinkles08, ASE Certified Technician
Category: GM
Satisfied Customers: 22815
Experience:  ASE Master and Advanced level certified. Factory trained with 15 years dealership experience
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I have a wiring issue and need help. I bought a 1991 v3500

Customer Question

I have a wiring issue and need help. I bought a 1991 v3500 with the 454. The truck will run but u have to run a hot wire to the brown wire with the black stripe on the egr solenoid to get it to crank. I replaced the egr solenoid and put a new connector on it and hooked it up correctly, but the tbi will not inject fuel unless u run a hot wire to the egr solenoid. When I bought the truck the orange wire to the oil sending unit had the brown wire attached to it and ruined the oil sending unit so I replaced it. Now I have oil pressure. All the wires to the egr solenoid were melted so my issue is probably going to be replacing the wiring harness to everthing if I can find one.
Submitted: 1 year ago.
Category: GM
Expert:  sprinkles08 replied 1 year ago.

Hello and welcome to JustAnswer!

You may just have a blown fuse. The EGR solenoid is on the same circuit as many other components, you applying power there is sending power throughout the rest of the circuit and allowing it to start. It's possible that you could have a wiring issue but I expect you just have a blown fuse, possibly due to the previous wiring damage.

Can you double check the 10a ECM/IG fuse?

Customer: replied 1 year ago.
That was the first thing I checked. I guess I will need to trace that brown wire down and see if it is broken. I was just wondering if something else would cause it other than a broke wire. Do u know what would cause those wires to melt like that. Only thing I can come with is a short but the fuse should blow if it is a short. I don't really want to make another wiring harness because finding all the connectors for the map, tbi, oil, temp, etc. is going to be almost impossible to find.
Expert:  sprinkles08 replied 1 year ago.

It has to be a broken/corroded wire or a loss of power at the fuse.

Wiring melted because of high current draw, assuming it wasn't from external heat.

Is there power at the fuse with the key on?

Customer: replied 1 year ago.
I have not checked for power at the fuse yet. That will be my next thing to do. Don't know why there would be a high draw of current there unless someone used a higher rated fuse than what it is called for. There was know external heat, but the egr valve may not be working correctly causing excess heat in the manifold and the solenoid was having to work to hard to keep up. I guess I will pull the egr valve and see how much carbon build up there is and replace it and trace the wire down and start looking for an engine wiring harness to replace mine.
Expert:  sprinkles08 replied 1 year ago.

If the EGR valve was stuck open or blown open by a restricted catalytic converter that could have caused enough heat to melt wiring in the close vicinity of the EGR valve.

If there is enough damage to the harness that it isn't repairable then you won't have a choice but to try and locate a harness, but as you've probably found most junkyards cut harnesses with no regard.

Before replacing or getting too deep in harness repair I would recommend seeing if the fuse has power.

Customer: replied 1 year ago.
The fuse has power. So I guess I will be tracing wires down. Maybe there is an after market wiring harness because I am sure there are none remaining at any of the chevy dealerships for that year model. Unless u have any other ideas I am going to assume that is my issue.
Expert:  sprinkles08 replied 1 year ago.

I expect the harness was discontinued some time ago. If there is power at the fuse and the fuse is good but there is no power on the circuit to any of the components then there is definitely a break or corroded spot in the wire. You'd either need to replace the harness or locate and repair the issue. Another way to fix it would be to run a new wire to each component on the circuit.

Customer: replied 1 year ago.
I went and checked the wires going to the egr module and all three wires have power going to them. Is that right? If they have power then the tbi should be working. Which one of these wires should be hot. I am confused because I did not think these wires had any power to them. Something obviously is not right.
Expert:  sprinkles08 replied 1 year ago.

I doubt the wires actually had power, if that was the case then applying power there wouldn't be allowing the engine to start. Either the wires didn't actually have power or the problem isn't present at this time, in which case the engine would start.